1. Technical Field
Exemplary embodiments in accordance with principles of inventive concepts relate generally to semiconductor integrated circuits, and more particularly to an analog-to-digital converter, an image sensor including the analog-to-digital converter and a method of operating an image sensor.
2. Discussion of the Related Art
Counters may be used in various electronic circuits, such as analog-to-digital converters (ADCs), for example. ADCs may, in turn, be used in devices for converting physical quantities such as light intensity, sound intensity, time, etc. into a digital signal. For exemplary, an image sensor, which captures images based on characteristics of semiconductor responding to intensity of incident lights, may include an analog-to-digital converter (ADC) for converting analog signals from a pixel array into digital signals. The ADC may include one or more counters that perform counting operation based on a clock signal.
Operation speed and power consumption of the counter may directly affect the performance of a device and/or a system including the counter. A complementary metal oxide semiconductor (CMOS) image sensor may include a relatively large number of counters to convert analog signals, which are output column by column from an active pixel sensor array, into digital signals. The number of counters increases as resolution of the image sensor increases. Unfortunately, as the number of counters increases and as the operational frequency of the image sensor increases in order to provide improved imaging, mismatches due to propagation delays of clock signals may degrade the operation of associated imaging devices.